I. Field of the Invention
This disclosure relates generally to systems, apparatus and methods for position location of devices, and more particularly to determining a position fix with radio measurements from base stations selected based on an indication of base station capacity.
II. Background
A satellite positioning system (SPS), such as the Global Positioning System (GPS), Galileo, and GLONASS, for example, typically provides position, velocity, and/or time information. In a particular implementation, an SPS may comprise a Global Navigation Satellite System (GNSS). A variety of receivers have been designed to decode signals transmitted from satellite vehicles (SVs) of an SPS to determine position, velocity, and/or time. In general, to decipher such signals and compute a final position, a receiver may first acquire signals from SVs that are in view, measure and track the received signals, and recover navigational data from the signals. By accurately measuring distances or “pseudoranges” to multiple SVs, a receiver may triangulate its position, e.g., solving for a latitude, longitude, and/or altitude. In particular, the receiver may measure distance by measuring the time that signals take to travel from a respective SV to the receiver.
In certain locations, such as indoor and urban environments with tall buildings, a receiver may only be able to acquire signals from three or fewer SVs. In such situations, the receiver may be unable to resolve all four variables of a position solution (including latitude, longitude, altitude, and time). If signals from fewer than four SVs are available, the receiver may be unable to calculate its position based on an SPS alone. To address such a limitation, receivers may employ non-SV positioning or hybrid location technology that involves signals from base station devices and/or access point devices of a wireless communication system. These receivers may measure times of wireless signals less processing delays to compute distances to base station devices and/or access point devices of a network.
In indoor environments, it may be desirable, and sometimes necessary, to know the location of a mobile device, terminal or cellular phone when SV signals are not available. The terms “location” and “position” are synonymous and are used interchangeably herein. For example, when indoors, a user may utilize the mobile device to browse through a website and may click on location sensitive content. The location of the mobile device may then be determined and used to provide appropriate content to the user. As another example, the user may place an emergency call using the mobile device. The location of the mobile device may then be determined and used to send emergency assistance to the user. There are many other scenarios in which knowledge of the location of the terminal is useful or necessary.
The indoor position of a mobile device may be estimated based on information gathered from various systems. Such systems may comprise a cellular network, a wireless wide access network (WWAN) communication system and/or a wireless local access network (WLAN) communication system comprising a number of base station devices or access point devices to support communications for a number of mobile devices. A position estimate for a mobile device may be obtained, for example, through triangulation or trilateration based on timing parameters such as round trip time signal delay, code phase detections, signal strength estimates, and/or other measurements obtained through communication with one or more base station devices or access point devices. A position estimate may be further based on known or reported locations of the base station devices and access point devices.